Re: [PATCH V2 1/3] perf/x86: Disable non generic regs for software/probe events

[Liang, Kan]

On 5/28/2019 4:56 AM, Peter Zijlstra wrote:
> On Mon, May 27, 2019 at 12:07:55PM -0700, kan.liang@xxxxxxxxxxxxxxx wrote:
> > diff --git a/arch/x86/include/uapi/asm/perf_regs.h b/arch/x86/include/uapi/asm/perf_regs.h
> > index ac67bbe..3a96971 100644
> > --- a/arch/x86/include/uapi/asm/perf_regs.h
> > +++ b/arch/x86/include/uapi/asm/perf_regs.h
> > @@ -52,4 +52,7 @@ enum perf_event_x86_regs {
> >   	/* These include both GPRs and XMMX registers */
> >   	PERF_REG_X86_XMM_MAX = PERF_REG_X86_XMM15 + 2,
> >   };
> > +
> > +#define PERF_REG_NON_GENERIC_MASK	(~((1ULL << PERF_REG_X86_XMM0) - 1))
> > +
> >   #endif /* _ASM_X86_PERF_REGS_H */
> > diff --git a/include/linux/perf_regs.h b/include/linux/perf_regs.h
> > index 4767474..1d794355 100644
> > --- a/include/linux/perf_regs.h
> > +++ b/include/linux/perf_regs.h
> > @@ -11,6 +11,11 @@ struct perf_regs {
> >   
> >   #ifdef CONFIG_HAVE_PERF_REGS
> >   #include <asm/perf_regs.h>
> > +
> > +#ifndef PERF_REG_NON_GENERIC_MASK
> > +#define PERF_REG_NON_GENERIC_MASK	0
> > +#endif
> > +
> >   u64 perf_reg_value(struct pt_regs *regs, int idx);
> >   int perf_reg_validate(u64 mask);
> >   u64 perf_reg_abi(struct task_struct *task);
> > @@ -18,6 +23,9 @@ void perf_get_regs_user(struct perf_regs *regs_user,
> >   			struct pt_regs *regs,
> >   			struct pt_regs *regs_user_copy);
> >   #else
> > +
> > +#define PERF_REG_NON_GENERIC_MASK	0
> > +
> >   static inline u64 perf_reg_value(struct pt_regs *regs, int idx)
> >   {
> >   	return 0;
>
> Much better than the last version; however..
>
> > diff --git a/kernel/events/core.c b/kernel/events/core.c
> > index abbd4b3..4865bdf 100644
> > --- a/kernel/events/core.c
> > +++ b/kernel/events/core.c
> > @@ -8457,6 +8457,12 @@ static void sw_perf_event_destroy(struct perf_event *event)
> >   	swevent_hlist_put();
> >   }
> >   
> > +static inline bool has_non_generic_regs(struct perf_event *event)
> > +{
> > +	return (event->attr.sample_regs_user & PERF_REG_NON_GENERIC_MASK) ||
> > +	       (event->attr.sample_regs_intr & PERF_REG_NON_GENERIC_MASK);
> > +}
> > +
> >   static int perf_swevent_init(struct perf_event *event)
> >   {
> >   	u64 event_id = event->attr.config;
> > @@ -8470,6 +8476,10 @@ static int perf_swevent_init(struct perf_event *event)
> >   	if (has_branch_stack(event))
> >   		return -EOPNOTSUPP;
> >   
> > +	/* Only support generic registers */
> > +	if (has_non_generic_regs(event))
> > +		return -EOPNOTSUPP;
> > +
> >   	switch (event_id) {
> >   	case PERF_COUNT_SW_CPU_CLOCK:
> >   	case PERF_COUNT_SW_TASK_CLOCK:
> > @@ -8633,6 +8643,10 @@ static int perf_tp_event_init(struct perf_event *event)
> >   	if (has_branch_stack(event))
> >   		return -EOPNOTSUPP;
> >   
> > +	/* Only support generic registers */
> > +	if (has_non_generic_regs(event))
> > +		return -EOPNOTSUPP;
> > +
> >   	err = perf_trace_init(event);
> >   	if (err)
> >   		return err;
> > @@ -8722,6 +8736,10 @@ static int perf_kprobe_event_init(struct perf_event *event)
> >   	if (has_branch_stack(event))
> >   		return -EOPNOTSUPP;
> >   
> > +	/* Only support generic registers */
> > +	if (has_non_generic_regs(event))
> > +		return -EOPNOTSUPP;
> > +
> >   	is_retprobe = event->attr.config & PERF_PROBE_CONFIG_IS_RETPROBE;
> >   	err = perf_kprobe_init(event, is_retprobe);
> >   	if (err)
> > @@ -8782,6 +8800,10 @@ static int perf_uprobe_event_init(struct perf_event *event)
> >   	if (has_branch_stack(event))
> >   		return -EOPNOTSUPP;
> >   
> > +	/* Only support generic registers */
> > +	if (has_non_generic_regs(event))
> > +		return -EOPNOTSUPP;
> > +
> >   	is_retprobe = event->attr.config & PERF_PROBE_CONFIG_IS_RETPROBE;
> >   	ref_ctr_offset = event->attr.config >> PERF_UPROBE_REF_CTR_OFFSET_SHIFT;
> >   	err = perf_uprobe_init(event, ref_ctr_offset, is_retprobe);
> > @@ -9562,6 +9584,10 @@ static int cpu_clock_event_init(struct perf_event *event)
> >   	if (has_branch_stack(event))
> >   		return -EOPNOTSUPP;
> >   
> > +	/* Only support generic registers */
> > +	if (has_non_generic_regs(event))
> > +		return -EOPNOTSUPP;
> > +
> >   	perf_swevent_init_hrtimer(event);
> >   
> >   	return 0;
> > @@ -9643,6 +9669,10 @@ static int task_clock_event_init(struct perf_event *event)
> >   	if (has_branch_stack(event))
> >   		return -EOPNOTSUPP;
> >   
> > +	/* Only support generic registers */
> > +	if (has_non_generic_regs(event))
> > +		return -EOPNOTSUPP;
> > +
> >   	perf_swevent_init_hrtimer(event);
> >   
> >   	return 0;
>
> I don't think this is anywhere near sufficient. What happens if we
> request XMM regs for an uncore PMU ?

Uncore PMU doesn't support sampling. It will return -EINVAL.
There is no regs support for counting. The request will be ignored.

I think current check for uncore is good enough.

Thanks,
Kan

> I'm thinking you want something along these lines...
>
> ---
> diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
> index a5436cee20b1..3ef1c2e0b177 100644
> --- a/arch/x86/events/intel/core.c
> +++ b/arch/x86/events/intel/core.c
> @@ -3281,7 +3281,13 @@ static int intel_pmu_hw_config(struct perf_event *event)
>   
>   		if (event->attr.sample_type & PERF_SAMPLE_CALLCHAIN)
>   			event->attr.sample_type |= __PERF_SAMPLE_CALLCHAIN_EARLY;
> -	}
> +
> +		/* we only support extended (XMM) registers for sample_regs_intr */
> +		if (event->attr.sample_regs_user & PERF_REGS_EXTENDED_MASK)
> +			return -EOPNOTSUPP;
> +
> +	} else if (has_extended_regs(event))
> +		return -EOPNOTSUPP;
>   
>   	if (needs_branch_stack(event)) {
>   		ret = intel_pmu_setup_lbr_filter(event);
> diff --git a/arch/x86/events/intel/ds.c b/arch/x86/events/intel/ds.c
> index 5e9bb246b3a6..4fae37f8c7c2 100644
> --- a/arch/x86/events/intel/ds.c
> +++ b/arch/x86/events/intel/ds.c
> @@ -2020,6 +2020,7 @@ void __init intel_ds_init(void)
>   					PERF_SAMPLE_TIME;
>   				x86_pmu.flags |= PMU_FL_PEBS_ALL;
>   				pebs_qual = "-baseline";
> +				x86_get_pmu()->capabilities |= PERF_PMU_CAP_EXTENDED_REGS;
>   			} else {
>   				/* Only basic record supported */
>   				x86_pmu.pebs_no_xmm_regs = 1;
> diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
> index 0ab99c7b652d..2bca72f3028b 100644
> --- a/include/linux/perf_event.h
> +++ b/include/linux/perf_event.h
> @@ -241,6 +241,7 @@ struct perf_event;
>   #define PERF_PMU_CAP_NO_INTERRUPT		0x01
>   #define PERF_PMU_CAP_NO_NMI			0x02
>   #define PERF_PMU_CAP_AUX_NO_SG			0x04
> +#define PERF_PMU_CAP_EXTENDED_REGS		0x08
>   #define PERF_PMU_CAP_EXCLUSIVE			0x10
>   #define PERF_PMU_CAP_ITRACE			0x20
>   #define PERF_PMU_CAP_HETEROGENEOUS_CPUS		0x40
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index abbd4b3b96c2..0c4872426b70 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -10064,12 +10064,16 @@ static int perf_try_init_event(struct pmu *pmu, struct perf_event *event)
>   		perf_event_ctx_unlock(event->group_leader, ctx);
>   
>   	if (!ret) {
> +		if (!(pmu->capabilities & PERF_PMU_CAP_EXTENDED_REGS) &&
> +		    has_extended_regs(event))
> +			ret = -EOPNOTSUPP;
> +
>   		if (pmu->capabilities & PERF_PMU_CAP_NO_EXCLUDE &&
> -				event_has_any_exclude_flag(event)) {
> -			if (event->destroy)
> -				event->destroy(event);
> +				event_has_any_exclude_flag(event))
>   			ret = -EINVAL;
> -		}
> +
> +		if (ret && event->destroy)
> +			event->destroy(event);
>   	}
>   
>   	if (ret)